See study results (link below) from 2008, which stated the following in its findings, though I still contend that a rotating propeller will Drive_You_Crazy: "The experimental results conﬁrm that a locked propeller produces greater drag than does a freewheeling screw (up to 100% more drag was observed, this being at higher speeds). Furthermore, for the freewheeling case, the magnitude of the hydrodynamic resistance is signiﬁcantly affected by the amount of frictional torque on the shaft, low torque being accompanied by low drag."